Got my first fisheye-lens today and wondered how it would perform. It's actually a zoom lens with focal length 10 to 17mm. At 10mm, it covers an angle of view of 180° diagonally over the frame.

A few pictures showing the typical fisheye effect at 10mm, 13mm and 17mm (all shot with Pentax K-5iis).

Focal length 10mm:

Focal length 13mm:

SMC Pentax-DA 10-17mm F3.5-4.5 fisheye-zoom, f/9.0, 1/500 s

Focal length 17mm:

And, for comparison, a picture of the same scene taken with a regular lens with a similar focal length of 18.3 mm (Ricoh GR):

Conclusions? The fisheye effect of the Pentax DA 10-17mm is somewhat less pronounced at the longer end of the zoom range but still well noticeable, especially when comparing it to a regular lens. Yes, it's true: one shouldn't use fisheye lenses for shooting of architectural scenes. But it's fun, at least for now.